Preheat oven to 375°F. Roll out dough and fit into pie dish, crimping edges. Prick bottom with fork.
Line crust with foil and fill with pie weights. Bake 15 minutes, then remove foil and weights. Bake 8-10 more minutes until lightly golden. Cool completely.
In a saucepan, combine cranberries, 1 cup sugar, orange juice, and zest. Boil, then simmer 8-10 minutes until cranberries burst.
Blend hot cranberry mixture until smooth, then strain through fine-mesh sieve, pressing to extract liquid. Return strained puree to saucepan.
Whisk egg yolks and cornstarch until smooth. Temper with 1/2 cup warm puree, then whisk back into saucepan. Cook over medium heat, whisking constantly, until thickened to pudding consistency, 3-4 minutes.
Remove from heat, stir in butter and a pinch of salt. Pour warm filling into cooled crust and smooth top. Preheat oven to 350°F.
In a clean bowl, beat egg whites with salt and cream of tartar until foamy. Gradually add remaining 1/4 cup sugar, beating until glossy stiff peaks form, 4-5 minutes. Beat in vanilla.
Spoon meringue over warm filling, spreading to crust edges. Create decorative peaks. Bake 12-15 minutes until golden, or torch until browned.
Cool at room temperature 1 hour, then refrigerate at least 2 hours before slicing. Use a sharp knife dipped in hot water for clean slices.